[petsc-users] Question about GAMG and memory use

[Barry Smith]

> On Mar 4, 2015, at 7:45 PM, Randall Mackie <rlmackie862 at gmail.com> wrote:
> 
> In my application, I am repeatedly calling KSPSolve with the following options:
> 
> -ksp_type gmres \
> -pc_type gamg \
> -pc_gamg_type agg \
> -pc_gamg_agg_nsmooths 1\
> 
> 
> each call is after the matrix and right hand side have been updated.
> 
> This works well in the sense that it solves the system in a reasonable number of steps, however, I have noticed that the memory footprint of the application increases by about 500 Mbytes after each call to KSPSolve (this is a big problem), and after several calls, I've maxed out the memory.
> 
> Is this expected behavior?

  No
> 
> I've combed through my code looking to make sure I don't have any memory leaks, and so far I haven't found any (doesn't mean there are not there).
> 
> However, when I use another PC, like jacobi, just to compare, I don't see this memory issue, or if I comment out that call to KSPSolve (there is a lot of other stuff going on in the code besides this call), I don't see this issue.
> 
> I've tried to destroy the KSP after each solve and recreate it each time, but there still seems to be some memory getting added.

   Run your program for a few solves with the command line option -malloc and after each call call to KSPSolve() put in a call to PetscMallocDump(). Take a look at the output and email it to us (this is best done with one process if you can; does the memory problem happen with 1 MPI process?).

   Barry

> 
> I've tried to distill this down to a smaller problem and test program, but so far I have been unsuccessful.
> 
> 
> Is there a way to completely release the memory associated with the GAMG preconditioner after a call to KSPSolve?
> 
> 
> Any other suggestions for tracking this down? I've run out of ideas.
> 
> 
> Thanks in advance,
> 
> Randy
> 
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> 
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